Ronaldo had earlier revealed that he was unhappy at Real Madrid and cited professional issues for not celebrating his 150th goal at the Bernabeu.
"I am sad and the club knows it, that's why I didn't celebrate the goals. The people in the club know why," Ronaldo said.
City are now pondering a move to bring the Portuguese back to Manchester with a sensational four-year contract next summer. The 27-year-old, who is paid around £250k weekly, has a buy-out clause of £100 million.
Roberto Mancini would have to clear his squad in order to raise funds for Ronaldo who still has three years left on his contract with the La Liga champions.
The former Red Devil, who was brought for a record £80m, led Real to the La Liga title scoring 46 goals in 38 league appearances and City cannot refuse to sign a player of his calibre who has scored 150 goals in 149 appearances for the Los Blancos.
Moreover, Ronaldo will have to accept a huge cut on his wages when Spain imposes higher income taxes from 7 per cent to 52 per cent.